Procedures for determination of in vivo concentrations of several trace elements in the surface enamel of human teeth are being developed and will be applied to extracted teeth prior to teeth in situ. Attempts will be made to develop topical fluoride solutions which will deposit fluoride in enamel primarily as fluorapatite rather than CaF2. The interaction of F with intact and carious enamel will be compared. The kinetics of the reaction 2Ca5OH(PO4)3 plus CaF2 yields 2Ca5F(PO4)3 plus Ca (OH)2 will be studied within the pH range of the mouth. Purification of the salivary protein which prevents intraoral hydrolysis of brushite will be undertaken. The characterization of the salivary proteins that show high affinity for hydroxy and fluorapatite will be completed and their adsorption isotherm and affinity constants will be determined. The ability of saliva proteins to alter the membrane properties of enamel will be studied in a model system. The ability of fluoride in fluoride treated enamel to interfere with the metabolism of cariogenic microorganisms (e.g. Streptococcus mutans) will be studied.